Conversation threading is a feature used by many email clients, bulletin boards, newsgroups, and Internet forums in which the software aids the user by visually grouping messages. Messages are usually grouped in a hierarchy by topic, with any replies to a message arranged visually near to the original message. A set of messages grouped in this way is called a topic thread or simply a thread. A discussion forum, e-mail client or news client is said to have "threaded topics" or a "threaded mode" if messages can be grouped in this manner.